Acute myocardial infarction commonly occurs when a thrombus or clot occludes an artery of the heart. When this occurs, a thrombolytic agent, such as streptokinase is used to obtain lysis of the clot.
It is known to use thrombolytic agents systemically by administering them intravenously. However, such use of streptokinase involves a considerable risk of bleeding in patients.
Alternatively, the streptokinase or other thrombolytic agent can be infused locally into the general region of the thrombus. This can be accomplished, for example, by utilizing an angiography catheter in a procedure which first involves injecting dye to locate the clot, terminating the dye injection and then utilizing that same catheter to infuse the thrombolytic agent in the general region of the thrombus. Unfortunately, the angiography catheter has too large a diameter to enable its distal opening to be positioned in close proximity to distal clots. Accordingly, the action of the thrombolytic agent is not as localized as desired, and the agent may be shunted away from the clot by collateral vessels. Also, to determine if the clot is dissolved, infusion must be stopped and the dye flow started. This increases the time to obtain removal of the clot and, therefore, increases the likelihood of necrosis of the myocardium.